First public commit.

lenser/a7800/viewer/assemble.py

@@ -0,0 +1,139 @@
+"""Assemble the Atari 7800 viewer with `xa` and lay out the 48K .a78 cartridge.
+
+MARIA reads the display-list list (DLL), the per-line display lists and the bitmap
+by DMA straight from cartridge ROM, so the packer just places them at fixed cart
+addresses and the viewer points MARIA at the DLL.
+
+ROM layout ($4000-$FFFF, 48K):
+    $4000  viewer code
+    $4100  colour register script (reg, value pairs, $FF-terminated)
+    $8000  bitmap        192 lines x 40 bytes (2bpp)
+    $A000  display lists  192 x 34 bytes (8 objects + end marker per line)
+    $BA00  DLL            192 x 3 bytes (one 1-line zone per line)
+    $FFFA  6502 vectors (NMI/RESET/IRQ -> $4000)
+"""
+from __future__ import annotations
+
+import os
+import shutil
+import struct
+import subprocess
+import tempfile
+
+VIEWER_DIR = os.path.dirname(os.path.abspath(__file__))
+
+CART_BASE = 0x4000
+CART_SIZE = 0xC000             # 48K
+SCRIPT_ADDR = 0x4100
+BITMAP_ADDR = 0x8000
+DL_BASE = 0xA000
+DLL_ADDR = 0xBA00
+
+WIDTH, LINES = 160, 192
+BYTES_PER_LINE = 40
+SEG_W_BYTES = 10               # 10 bytes = 40 px per object
+N_SEG = 4
+SEG_W_PX = 40
+DL_LEN = N_SEG * 4 + 2         # 4 objects (4 bytes) + 2-byte end = 18
+
+# MARIA colour-register addresses in the order the converter emits them:
+# BACKGRND, then P0C1..P0C3, P1C1.., ... P7C1..P7C3.
+COLOR_REGS = [0x20]
+for _p in range(8):
+    COLOR_REGS += [0x21 + 4 * _p, 0x22 + 4 * _p, 0x23 + 4 * _p]
+
+
+class AssemblerError(RuntimeError):
+    pass
+
+
+def have_xa() -> bool:
+    return shutil.which("xa") is not None
+
+
+def _assemble() -> bytes:
+    if not have_xa():
+        raise AssemblerError("The 'xa' (xa65) assembler was not found on PATH.\n"
+                             "Install it with:  sudo apt install xa65")
+    wrapper = (f"#define SCRIPT ${SCRIPT_ADDR:04X}\n"
+               f"#define DLL ${DLL_ADDR:04X}\n"
+               '#include "viewer.s"\n')
+    with tempfile.TemporaryDirectory() as td:
+        out = os.path.join(td, "v.bin")
+        fd, wrap = tempfile.mkstemp(suffix=".s", prefix="_wrap_", dir=VIEWER_DIR)
+        try:
+            with os.fdopen(fd, "w") as f:
+                f.write(wrapper)
+            proc = subprocess.run(["xa", "-o", out, os.path.basename(wrap)],
+                                  capture_output=True, text=True, cwd=VIEWER_DIR)
+            if proc.returncode != 0:
+                raise AssemblerError(f"xa failed:\n{proc.stdout}{proc.stderr}")
+            with open(out, "rb") as f:
+                return f.read()
+        finally:
+            os.unlink(wrap)
+
+
+def _a78_header(rom_len: int, title: str) -> bytes:
+    h = bytearray(128)
+    h[0] = 1                                   # header version
+    h[1:1 + 9] = b"ATARI7800"
+    h[17:17 + 32] = title.encode("ascii", "replace")[:32].ljust(32, b"\x00")
+    h[49:53] = struct.pack(">I", rom_len)      # ROM size (excl. header)
+    # cart type 0 = plain linear; controllers = joystick; NTSC
+    h[55] = 1
+    h[56] = 1
+    h[57] = 0
+    h[100:100 + 28] = b"ACTUAL CART DATA STARTS HERE"
+    return bytes(h)
+
+
+def build_cart(data: bytes, title: str = "8bitlenser") -> bytes:
+    """data = converter blob: bitmap(7680) + seg_palettes(192*8) + colours(25)."""
+    bitmap = data[:LINES * BYTES_PER_LINE]
+    seg_pal = data[LINES * BYTES_PER_LINE:LINES * BYTES_PER_LINE + LINES * N_SEG]
+    colours = data[LINES * BYTES_PER_LINE + LINES * N_SEG:]
+
+    code = _assemble()
+    rom = bytearray(b"\x00" * CART_SIZE)
+
+    def place(addr, blob):
+        off = addr - CART_BASE
+        rom[off:off + len(blob)] = blob
+
+    place(CART_BASE, code)
+
+    # colour register script: (reg, value) pairs, $FF terminator
+    script = bytearray()
+    for reg, val in zip(COLOR_REGS, colours):
+        script += bytes([reg, val])
+    script.append(0xFF)
+    place(SCRIPT_ADDR, script)
+
+    place(BITMAP_ADDR, bitmap)
+
+    # per-line display lists (8 objects of 5 bytes, each its own palette)
+    dls = bytearray()
+    for line in range(LINES):
+        for s in range(N_SEG):
+            gfx = BITMAP_ADDR + line * BYTES_PER_LINE + s * SEG_W_BYTES
+            pal = seg_pal[line * N_SEG + s] & 0x07
+            width = (-SEG_W_BYTES) & 0x1F      # two's-complement byte count
+            dls += bytes([gfx & 0xFF, (pal << 5) | width, gfx >> 8, s * SEG_W_PX])
+        dls += bytes([0x00, 0x00])             # end of DL
+    place(DL_BASE, dls)
+
+    # display-list list: one 1-line zone per line
+    dll = bytearray()
+    for line in range(LINES):
+        dl = DL_BASE + line * DL_LEN
+        dll += bytes([0x00, dl >> 8, dl & 0xFF])   # offset 0 (1 line), DL hi, lo
+    place(DLL_ADDR, dll)
+
+    # 6502 vectors -> viewer entry ($4000)
+    for v in (0xFFFA, 0xFFFC, 0xFFFE):
+        off = v - CART_BASE
+        rom[off] = CART_BASE & 0xFF
+        rom[off + 1] = CART_BASE >> 8
+
+    return _a78_header(len(rom), title) + bytes(rom)